Radiofrequency communication is a mode of communication that is increasingly used to connect electronic devices to each other. For information, the use of interfaces of the Bluetooth, Wi-Fi (standard IEEE 802.11) ZigBee (standard IEEE 802.15.4) or other types is known for exchanging data between a computer, a telephone, a camera, a printer or other peripheral devices. To simplify the use of the different devices, the utilization of the provision of services that are visible to the other devices through the radiofrequency interface is known. “Service” here means an application that makes it possible to have controlled access to one or more resources of the communication device.
For example, a printer with a Wi-Fi interface will regularly emit a message to propose a printing service. The printing service consists in printing a file that has been sent to it. A device such as a laptop computer or a camera with an interface of the same type that is located in the emission range of the printer may inform its user that the printing service is available. The user may then decide to print on the printer from the device.
The idea of service may also be seamless for the user. That is the case with terminals providing access to an information network, where transactions for logging on to the network take place without any intervention from the user. That is the case for example with user authentication services via a communicating device or simply with access to a data network.
The same communication device may be associated with different services. For example, a Personal Digital Assistant or PDA with an interface of the Wi-Fi or Bluetooth type may have a service for automatic connection to a network server for synchronization, an authentication service to identify the user of the PDA when they use another computer or exchange data with another PDA, a location service to locate the user within a site and/or receive widely broadcast messages. Several other examples are possible with the multiplication of device functionalities, such as a multimedia telephone that also performs the functions of music player and camera, while allowing use for payment transactions.
Currently, many digital communication devices use only one physical transmission channel divided into logical channels, where each logical channel supports a service that is associated with it. The logical channels are thus multiplexed in the same physical channel. In general, the physical channel is configured to guarantee minimum reception quality while guaranteeing the minimum emission power suited to all the services.
A problem occurs when simultaneous use is made of services that need to be limited to a certain distance, while offering services that require communication over a longer distance at the same time.